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Table 3 The point mutation in the QRDR of gyrA of nalidixic acid-resistant Salmonella.

From: Genetic Diversity of Salmonella enteric serovar Typhi and Paratyphi in Shenzhen, China from 2002 through 2007

Point mutation in the QRDR of gyrA MIC (μg/mL)*
  nalidixic acid ciprofloxacin
nalidixic acid-resistant S. typhi   
   Ser83→Phe (TCC→TTC) ≥ 256 (9) 0.06 (4), 0.125 (1), 0.25 (2), 0.5 (2)
   Asp87→Gly (GAC→GGC) 128 (1) 0.06 (1)
   Asp87→Asn (GAC→AAC) 64 (2), ≥ 256 (1) 0.06 (2), 0.25 (1)
nalidixic acid-resistant S. paratyphi A   
   Ser83→Phe (TCC→TTC) ≥ 256 (59) 0.25 (8), 0.5 (50), 1 (1)
   Ser83→Pro (TCC→CCC) 32 (2) 0.125 (1), 0.03 (1)
nalidixic acid-resistant S. paratyphi C   
   Ser83→Tyr (TCC→TAC) ≥ 256 (1) 0.125 (1)
  1. * parentheses referring to the number of isolates with the point mutation in the QRDR of gyrA